Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$74.64	9.342%	$81.6129	$81.61	$81.60	$81.60
Purchase #2	$74.84	4.434%	$78.1584	$78.16	$78.15	$78.20
Purchase #3	$200.67	10.422%	$221.5838	$221.58	$221.60	$221.60
Purchase #4	$181.66	13.480%	$206.1478	$206.15	$206.15	$206.10
Purchase #5	$156.66	10.814%	$173.6012	$173.60	$173.60	$173.60
Purchase #6	$96.65	6.680%	$103.1062	$103.11	$103.10	$103.10
Purchase #7	$187.52	9.683%	$205.6776	$205.68	$205.70	$205.70
7 purchase totals =	$972.64		$1,069.8879	$1,069.89	$1,069.90	$1,069.90